Galactic Dynamos — a Challenge for Observers
نویسندگان
چکیده
منابع مشابه
Galactic Dynamos and Galactic Winds
Spiral galaxies host dynamically important magnetic fields which can affect gas flows in the disks and halos. Total magnetic fields in spiral galaxies are strongest (up to 30 μG) in the spiral arms where they are mostly turbulent or tangled. Polarized synchrotron emission shows that the resolved regular fields are generally strongest in the interarm regions (up to 15 μG). Faraday rotation measu...
متن کاملAccretion and galactic dynamos
We show that radial flows (directed either inward or outward) suppress mean-field dynamo action in a thin disc. Under conditions typical of spiral galaxies, the reduction in the growth rate of the large-scale magnetic field can reach 25–30%. The dynamo-generated galactic magnetic fields themselves can drive radial flows at a rate of order 0.1M yr−1. These radial flows can contribute to the satu...
متن کاملSimulations of Galactic Dynamos
We review our current understanding of galactic dynamo theory, paying particular attention to numerical simulations both of the mean-field equations and the original three-dimensional equations relevant to describing the magnetic field evolution for a turbulent flow. We emphasize the theoretical difficulties in explaining non-axisymmetric magnetic fields in galaxies and discuss the observationa...
متن کاملIntroduction to galactic dynamos
Galaxies are attractive objects to study. The magnetism of their natural beauty adds to the fascinating diversity of physical processes that occur over an enormous range of scales from the global dimension of order 10 kpc down to the viscous turbulent scales of 1000 km and less. The visual image of a galaxy (see Fig. 1) is dominated by the optical light mostly produced by stars that contribute ...
متن کاملGalactic and Accretion Disk Dynamos
Dynamos in astrophysical disks are usually explained in terms of the standard alpha-omega mean field dynamo model where the local helicity generates a radial field component from an azimuthal field. The subsequent shearing of the radial field gives rise to exponentially growing dynamo modes. There are several problems with this model. The exponentiation time for the galactic dynamo is hard to c...
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ژورنال
عنوان ژورنال: Symposium - International Astronomical Union
سال: 1993
ISSN: 0074-1809
DOI: 10.1017/s0074180900174297